CVE-2026-96252 in Windows
Summary
by MITRE • 10/15/2026
Improper verification of cryptographic signature in Active Directory Federation Services (AD FS) allows an unauthorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 10/15/2026
Active Directory Federation Services serves as a critical component in enterprise identity management, facilitating single sign-on and secure authentication across organizational boundaries by relying heavily on the integrity of digital signatures within Security Assertion Markup Language tokens. The vulnerability described involves a fundamental failure in the verification process for these cryptographic signatures, which are essential to ensuring that assertions originate from trusted identity providers and have not been tampered with during transit. When an application fails to rigorously validate the signature against the expected public key or certificate chain, it creates a significant trust boundary violation where malicious actors can forge valid-looking authentication tokens without possessing the private keys associated with legitimate services.
This flaw effectively neutralizes one of the primary security controls designed to prevent identity spoofing and session hijacking within federated environments. An unauthorized attacker capable of intercepting network traffic or injecting packets into the communication channel between a service provider and an identity provider can craft malicious assertions that appear authentic due to the lack of strict signature verification. By manipulating these tokens, the adversary can impersonate legitimate users, escalate privileges by altering role-based access claims within the assertion, or bypass multi-factor authentication requirements if those are embedded in the token payload rather than enforced at the network level. The operational impact is severe, potentially leading to unauthorized access to sensitive corporate resources, data exfiltration, and a complete compromise of the organization's identity infrastructure integrity.
From a classification perspective, this vulnerability aligns with CWE-347 which denotes Improper Verification of Cryptographic Signature, highlighting the root cause as a logic error in the validation routine rather than a weakness in the cryptographic algorithm itself. In terms of adversary tactics, this exploitation vector maps directly to ATT&CK technique T1606 Forge Web Credentials, where attackers create fake credentials or tokens to gain access to web applications and services without needing valid user accounts. It also intersects with T1498 Network Denial of Service if the spoofing is used to disrupt service availability by flooding systems with invalid but structurally correct requests that consume processing resources before being discarded at later stages, though the primary threat remains unauthorized access via credential forgery.
Mitigation strategies must focus on ensuring strict adherence to cryptographic verification standards within the AD FS configuration and codebase. Administrators should verify that all relying party trusts are configured to require signature validation for SAML assertions and that only trusted certificates with valid chain-of-trust paths are accepted as signing authorities. Regular auditing of certificate expiration dates is crucial, as expired or revoked certificates can sometimes lead to fallback behaviors that weaken security posture if not explicitly disabled. Furthermore, implementing network-level protections such as mutual TLS authentication between federation servers can add a layer of defense-in-depth by ensuring the identity of the communicating parties before any token processing occurs. Organizations should also apply all available Microsoft updates and patches related to AD FS cryptographic handling, as vendors often release hotfixes that enforce stricter validation logic or disable legacy protocols that may be susceptible to such spoofing attacks. Continuous monitoring for anomalous authentication patterns originating from unexpected IP addresses or using unusual certificate fingerprints can help detect exploitation attempts in real-time before significant damage occurs.